• The Journal of Korean Physical Therapy
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• v.18 no.4
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• pp.51-60
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• 2006

Purpose: This study was to compare the effect of center of pressure(COP) displacement and muscle activation onset during expected and unexpected sudden limb loading in subjects with low back pain and healthy control subjects. Most studies of COP displacement and muscle activation onset on postural task focused on sudden trunk loading or gross limb movements. Investigation of the COP displacement and muscle activation onset during expected and unexpected sudden upper limb loading deserves similar attention. Methods: For this study, 14 subjects with low back pain and 12 healthy control subjects are participated. Force plate and surface EMG measures were used to determine COP displacement and muscle activation onset under expected and unexpected sudden upper limb loading. Results: COP displacement and muscle activation onset under unexpected sudden upper limb loading were similar in subjects with low back pain and healthy control subjects. However, COP displacement and muscle activation onset under expected sudden upper limb loading were shortened in healthy control subject but not among the subjects with low back pain. Conclusion: The results provide evidence for impaired feed-forward control in subjects with low back pain.

• Journal of the Korean Society of Physical Medicine
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• v.5 no.1
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• pp.15-24
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• 2010

Purpose : The purpose of this study was to investigate the effect of loading position on plantar center of pressure(COP) displacement when carrying a schoolbag during walking. Methods : Forty-four normal subjects were randomly assigned to five groups according to the method of carrying a schoolbag. The carrying a schoolbag methods were classified into five conditions: no bag (condition 1), a backpack (condition 2), a shoulder bag (condition 3), a cross bag (condition 4), a one-hand bag (condition 5). COP displacement such as anteroposterior distance and mediolateral distance of COP were measured with F-scan system. The repeated one-way analysis of variance (ANOVA) and independent t-test were used to confirm the statistical significance. Results : In the comparison of parameters of COP displacement between conditions, anteroposterior distance and mediolateral distance in the left foot and mediolateral distance in the right foot were not significantly different(p>.05), but anteroposterior diatance in the right foot was significantly different(p>.05). Between left and right foot, at condition 1 and 5 the mediolateral distance of COP was significantly different(p<.05) but anteroposterior distance at condition 1 and 5, anteroposterior distance and mediolateral distance of COP at condition 2, 3 and 4 were not significantly different(p>.05). Conclusion : These findings showed that the various loading position by five types of carrying a schoolbag didn't have influence significantly on COP displacement on during walking because of mechanism of postural adaption.

• The Journal of Korean Physical Therapy
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• v.21 no.3
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• pp.75-80
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• 2009

Purpose: The purpose of this study was to examine the effect of an obstacle height on the balance control of older adults while stepping over an obstacle from a position of quiet stance. Methods: Fifteen community-dwelling healthy older adults (mean age, $74.4\pm4.27$ yrs; age range, 67-82 yrs) volunteered to participate in this study. The subjects performed gait initiation (GI) and they stepped over obstacles of two different heights (10 cm and 18 cm) at a self-paced speed from a position of quiet stance. Their performance was assessed by recording the changes in the displacement of the COP in the anteroposterior (A-P) and mediolateral (M-L) directions using a force platform. Results: The M-L displacement of the COP significantly increased for an 18 cm obstacle height condition as compared to the GI and a 10 cm obstacle height condition (p<0.01). Furthermore, the M-L displacement of the COP for a 10 cm high obstacle was significantly greater for that for the GI (p<0.01). However, the mean of the A-P displacement of the COP was similar between the stepping conditions for the A-P displacement of the COP (p>0.05). Conclusion: This study suggests that the M-L COP displacement could be a better parameter to identify the dynamic balance control in older adults when negotiating obstacles.

• The Journal of Korean Physical Therapy
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• v.23 no.2
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• pp.1-5
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• 2011

Purpose: This study examined the difference in the center of pressure (COP) displacement time in older adults according to the obstacle height during stance at each sub.phase when crossing obstacles. Methods: Fifteen older adults were enrolled in this study (${\geq}65$ years of age). The F-scan was used to measure the COP displacement time when crossing a 0, 10 and 40cm obstacle, and the stance phase was divided into 4 sub-phases according to the foot contact pattern. Results: During the stance phase, the COP displacement time increased with increasing obstacle height. During the mid-stance, terminal stance and pre-swing except for the loading response, there were significant differences in the COP displacement time according to the obstacle height. Conclusion: This study suggests that older adults show differences in the COP displacement time according to the stance sub-phase while crossing obstacles, and they use different mechanisms according the sub-phases to maintain balance during obstacle crossing.

• The Journal of Korean Physical Therapy
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• v.23 no.3
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• pp.1-5
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• 2011

Purpose: This study examined the relationship between the center of pressure (COP) displacement time during the stance phase and dynamic balance ability when older adults cross a 10 cm obstacle. Methods: Fifteen older adults were enrolled in this study (all ${\geq}65$ years of age). The F-scan was used to measure the COP displacement time when subjects cross a 10 cm obstacle, and the Dynamic gait index. Berg's balance scale and the Four square step test were used to measure dynamic balance ability. Results: The Dynamic gait index, Berg's balance scale and the Four square step test were correlated with each other. Dynamic balance ability was correlated with COP displacement time during the stance phase at an obstacle crossing in older adults. Conclusion: People with higher dynamic balance ability show a smaller COP displacement time during the stance phase at an obstacle crossing. Therefore, dynamic balance ability can be predicted by measuring the center of pressure displacement time.

• Physical Therapy Korea
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• v.12 no.1
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• pp.11-21
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• 2005

The purpose of this study was to investigate how COP displacement of a hemiplegic foot in stance phase during gait is related to clinical balance measures and the recovery stage in hemiplegic stroke patients. Twenty-eight functionally ambulant hemiplegic patients who had suffered from strokes and thirty age-matched healthy subjects participated in this study. COP parameters were calculated. Clinical balance was measured using the Functional Reach Test (FRT) and Timed Up and Go Test (TUGT). The recovery stage, proprioception, and clonus of the ankles or lower extremities were also measured for physical impairment status. The COPx max-displacement in the medial-lateral side of the stroke patients was significantly longer than that of the normal group (p=.038). The COPy max-displacement in the anterior-posterior side of the stroke patients was significantly shorter than that of normal group (p<.001). Significant differences in the COPx and COPy displacement asymmetry index were found between the two groups (p<.01). The FRT was correlated with the COPx displacement (r=.552) and COPy displacement (r=.765). The TUGT was correlated with the COPy displacement (r=-.588) only. The recovery stage of the lower extremities was correlated with COPy displacement (r=.438). The results of the study indicate that the characteristic of COP displacement in hemiplegic feet in stance phase during gait is related to balance ability and recovery in stroke patients. COP parameters acquired by the mapping of foot pressure in stance phase during gait will provide additional useful clinical information. This information can be used by clinicians to assess objectively the pathologic gait with other diseases and to evaluate the therapeutic effects on gait in stroke patients.

• The Journal of Internal Korean Medicine
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• v.36 no.4
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• pp.478-485
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• 2015

Objectives: The purpose of this study was to analyze the change of area and average velocity of the center of pressure (COP) according to gait improvement in post-stroke hemiplegic patients.Methods: We measured the area and the average velocity of COP displacement of ten post-stroke hemiplegic patients while they stood quietly on a force plate at the time of dependent and independent gait . We also measured the area and the average velocity of COP displacement of normal persons to verify differences between them and post-stroke hemiplegic patients.Results: The area of COP displacement decreased significantly, and the average velocity of COP displacement tended to decrease, but not significantly. There were significant differences in the area and the average velocity of COP displacement between post-stroke hemiplegic patients and normal persons.Conclusions: The results of this study show that postural control ability improves as gait improves.

• The Journal of Korean Physical Therapy
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• v.22 no.1
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• pp.47-51
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• 2010

Purpose: The purpose of this study was to determine whether there are any differences, with and without a toe spreader (TS), in dynamic foot pressure distribution in children with spastic diplegic cerebral palsy. Methods: Dynamic foot pressure recording using the RSscan system were obtained during walking in 12 participants (male=7, female=5) with and without TS. Mean force was measured for four different plantar regions; great toe, forefoot, midfoot, hindfoot. Displacement of center of pressure (COP), velocity of COP displacement and stance time were also measured during gait. Results: TS walking exhibited statistically significant decrease of mean force under great toe and forefoot (p<0.05), compared with a barefoot walking. Also, TS walking exhibited statistically significant increase of antero-posterior displacement of COP (p>0.05). Conclusion: These findings indicate the potential clinical utility of toe spreader to correct dynamic foot pressure during stance phase in children with spastic diplegic cerebral palsy.

• Physical Therapy Korea
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• v.15 no.4
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• pp.27-33
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• 2008

The purpose of this study was to investigate the changes of the center of pressure (COP) trajectory in healthy elderly subjects while crossing an obstacle before and after participation in Tai Chi training. Forty healthy elderly subjects participated either in a 12-week intervention of Tai Chi training or in a health education program. The participants were divided into two groups (the experimental group and the control group). Subsequently, the participants were pre- and post-tested on crossing over an obstacle from a quiet stance. Participants in the experimental group received Tai Chi training that emphasized the smooth integration of trunk rotation, a shift in weight bearing from bilateral to unilateral support and coordination and a gradual narrowing of the lower-extremity stance three times weekly. The participants in the control group attended a health education program one hour weekly and heard lectures about general information to promote health. Performance was assessed by recording the changes in the displacement of the COP in the anteroposterior (A-P) and mediolateral (M-L) directions using a force platform. Participants in the Tai Chi group significantly increased the A-P and M-L displacement of the COP after Tai Chi training (p<.05). No significant differences in the A-P and the M-L displacement of the COP between pre-testing and post-testing in the control group were found. This study has shown that participation in Tai Chi exercise increased the magnitude of the A-P and M-L displacement of the COP, thereby improving the ability of healthy elderly participation to generate momentum to initiate gait. These findings support the use of Tai Chi training as an effective fall-prevention program for the elderly.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1211-1214
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• 2004

High-heeled women have been identified with balance control problems. The purposes of this study were to objectively quantify the displacements and velocities of center-of-pressure (COP) of body during waist pulling and to compare the differences between barefooted and high-heeled situations. We used a waist pulling system which has three different magnitudes to sway the subjects. We found that the kinematic information of barefooted and high-heeled women's COP is very important in understanding the mechanism of postural balance control of women in every-day life. In the high-heeled's case, the displacement of COP increases in 200％ as against bare footed. Also the velocity variation of COP grows three times than the bare footed. COP analysis in postural balance study of high-heeled women is also considered useful in development of the safety systems that prevent high-heeled women from falling